We investigate the supernova remnant (SNR) 3C 397 and its neighboring pulsar PSR J1906+0722 in high energy gamma rays by using nearly six years of archival data of Large Area Telescope on board Fermi Gamma Ray Space Telescope (Fermi-LAT). The off-pulse analysis of gamma-ray flux from the location of PSR J1906+0722 reveals an excess emission which is found to be very close to the radio location of 3C 397. Here, we present the preliminary results of this gamma-ray analysis of 3C 397 and PSR J1906+0722.

W49B is a mixed-morphology supernova remnant (SNR) with the presence of enhanced abundances and overionization confirmed by X-ray observation. For the overionization, a strong radiative recombination continuum (RRC) has been detected and confirmed by SUZAKU and XMM-Newton. Here, we investigate these intriguing observational results through a multidimensional hydrodynamic model that takes into account, for the first time, the mixing of ejecta with the circumstellar and interstellar medium, thermal conduction, and non-equilibrium ionization. The model can reproduce the morphology and the overionization pattern of W49B. We found that the overionized plasma originates from the rapid cooling of the hot plasma originally heated by the shock reflected from the dense ring-like cloud. In addition, based on the most updated ATOMDB (v2.0.2), we calculated the spectrum of one cell in the overionized region from the simulation results at present. We got the overionized spectrum that is in agreement with the observational results. Thus, our primary result indicates that the model is consistent with the observations both spatially and spectrally.

Three-dimensional kinematic reconstructions of optically emitting ejecta in the young Galactic supernova remnant Cassiopeia A (Cas A) are discussed. The reconstructions encompass the remnant's faint outlying ejecta knots, including the exceptionally high-velocity NE and SW streams of debris often referred to as ‘jets’. The bulk of Cas A's ejecta are arranged in several circular rings with diameters between approximately 30″ (0.5 pc) and 2′ (2 pc). We suggest that similar large-scale ejecta rings may be a common phenomenon of young core-collapse remnants and may explain lumpy emission line profile substructure sometimes observed in spectra of extragalactic core-collapse supernovae years after explosion. A likely origin for these large ejecta rings is post-explosion input of energy from plumes of radioactive 56Ni-rich ejecta that rise, expand, and compress non-radioactive material to form bubble-like structures.

Since the discovery of nonthermal X-rays in the shell-type supernova remnant SN1006 almost 20 years ago, the field has developed considerably, owing significant progress to our understanding of particle acceleration. Key to the characterization of the nonthermal emission is the ability of current satellites, XMM-Newton and Chandra, to perform spatially resolved spectroscopy at a relatively small spatial scale.

In this review, I intend to present the main contributions of the study of nonthermal X-rays from supernova remnants to the understanding of particle acceleration.

The evolutionary phases in going from a Type Ia supernova explosion to a 1000-yr-old remnant are reviewed. The explosion sets up the density and composition structure of the ejecta and can have radiative effects on the surroundings. The early shock interactions may be observable at radio and X-ray wavelengths if the circumstellar density is sufficiently high. The later interaction with the interstellar medium is affected by the collisionless shock physics and hydrodynamic instabilities.

Owing to the rapid progress of space sciences and the high-energy astrophysics in the past 2–3 decades, historical supernova records have made important contributions to modern astrophysics and will continue to do so in the future. The main topics here are the earliest supernova observed by human beings and the AD393 guest star as well as our new concept of “Po stars”